Tests Of The Extended Range SRF Cavity Tuners For The LCLS-II-HE Project*

TL;DR

This paper reports on tests of extended-range superconducting RF cavity tuners for the LCLS-II-HE project, demonstrating significant frequency shifts in cryomodule environments to support multi-energy beam production.

Contribution

It introduces and verifies the effectiveness of off-frequency detune mode operation of SRF tuners in cryomodule testing for the LCLS-II-HE project.

Findings

Achieved a frequency shift of -565±80 kHz in tests

Demonstrated successful tuner operation during assembly and testing

Provided procedures for tuner setting during assembly

Abstract

The LCLS-II HE superconducting linac can produce multi-energy beams by supporting multiple undulator lines simultaneously. This could be achieved by using the cavity SRF tuner in the off-frequency detune mode. This off-frequency operation method was tested in the verification cryomodule (vCM) and CM 1 at Fermilab at 2 K. In both cases, the tuners achieved a frequency shift of -565$\pm$80 kHz. This study will discuss cavity frequency during each step as it is being assembled in the cryomodule string and finally when it is being tested at 2 K. Tracking the cavity frequency helped enable the tuners to reach this large frequency shift. The specific procedures of tuner setting during assembly will be presented.